Over ocean radio transmitter/receiver device

[hybridmetta]

Hi everyone. Im trying to build a circuit that will be used for long range communication... and by long.... i mean over the ocean :roll: . Im living in Portugal and this circuit is suposed to have a range of around 6000 km.

I have some ideas on how to do it and i have some ppl helping me but i guess i still need some "superior" help.

Well the brain of this circuit will be a pic16f877 microcontroller. it will have an lcd similar to the ones inside nokia 3310 phones, an ftdi chip for communication with the chip using the usb port of a computer (if possible i would also like to be able to update the firmware of this pic using this same port) and possibly a max1811 chip to recharge a lithium battery.
cuz i need to transmit and receive at the same time maybe i need two diferent oscillators and amplifiers. the oscillators are vco controlled by the pic16f877 using some kind of DAC.

After all this is done, the circuit will obviously have either headphones output or a speaker attached, a microphone, buttons, leds an all that neat stuff.

the obvious problems are... how am i suposed to make a vco stable enough for such a long range communication? how should i place the filter to reduce the noise on the receiving frequency? what kind of antenna should i use? if i have to use 2 antennas... how can i predict the way they will interact? how much power do i need? will a lithium battery do the job? is it better if i use a frequency in hf or some other band? how can i predict the propagation of the waves in this circuit based on the solar flux (considering that i will use hf)? how powerfull should the amplifier be? the vco comes before or after the amplifier? is it legal to use hf to communicate this far without a licence?

i have lots of issues in the structure of this device... and im sure this will take me a long long time to build... still... i wanna try it.

Anyone knows any source where i can look for some info on this subject?

Just in case someone has any doubts on this kind of long range communication... well it was already proved to be possible by marconi in 1901 when he made the first device to communicate over the ocean.

ps: i read on the net that maybe i will have to use a device capable of delivering round 1kw of power? how can i possibly get all that power? it seems to be impossible... at least for a simple electronic hobbies...

Well thanks in advance for any answer that might help me to find a path to build this device.

 

[audioguru]

Communicate over the internet. :lol:

 

[upand_at_them]

HF radio. Get a ham license.

Mike

 

[zevon8]

Just in case someone has any doubts on this kind of long range communication... well it was already proved to be possible by marconi in 1901 when he made the first device to communicate over the ocean.

If you attempt anything like Marconi did, you will create a mob scene reminiscent of the old Frankenstein movies where the townsfolk come to lynch the source of their grief. His basically uncontrolled broad spectrum transmitting of noise at high power will cause untold interference in todays communications devices. I doubt the authorities would be very impressed either. Amateur radio and spectrum useage is regulated and licenced.

 

[john1]

Hi hybridmetta,

I used to use a CB set to chat to people in many other countries.
That was a long time ago now, when they were AM.
Its output power was in the area of about seven watts.
I'm not sure of the frequencies of those old CB sets, i think it was
around twenty megs ... maybe ... ?

Quote:
is it legal to use hf to communicate this far without a licence?

The law usually limits the output power allowed, and usually prohibits
certain frequency ranges. You may or may not need a license to use
certain set-ups.

If you intend to recieve and send at the same time, then yes you will
need seperate equipment for sending and recieving.

The stability of any VCO used is unlikely to be a factor in the long
range communication.

These set-ups are usually crystal controlled, i don't think that straight
LC tanks have sufficient 'rejection', as adjacent signal slots are
quite close frequency-wise. I think about 200 Kc apart, but i'm not sure,
could be closer.

Don't worry too much about solar flux.

Marconi's set-up was extremely primitive, and used a type of wave generator
that would not be allowed these days, as its output was very coarse and
would interfere with almost anyhing capable of recieving a signal.
Although i believe its output was tuned, so its main output was at the
intended frequency. There was very little else around to object, unlike
today.
It has often been disputed whether or not a signal was actually recieved,
one or two unsucessfull attempts at getting a simple crystal set to
respond over 2000 miles have been tried, so far without success.
But i would like to think that a signal was recieved.

You shouldn't need anything like a kilowatt, seven or eight watts should
be enough. You may find that you don't need any licensing if you keep
the wattage low, and stick to frequencies set aside for radio controlled
toys and such. Check up on your local regulations.

Best of luck with it, John


Regards, John

 

[Nigel Goodwin]

is it legal to use hf to communicate this far without a licence?

No! - it's illegal in pretty well every country in the world - and if there's any country where it's not, they would probably just shoot you instead!.

Your requirements are EXTREMELY difficult to meet, and will only be possible under certain conditions at certain times of the day, and even certain times of the year, or certain solar cycles (many years).

You are also likely to need considerable power, the CB suggestion over long distances ONLY works during high points of the sunspot cycle, a condition known as 'skip' (I 'think' this is every seven years or so?, and short term).

You obviously know nothing about radio?, so I would suggest for a start that you go and do your RAE (Radio Amateurs Exam), and take out a ham licence - however, this probably wouldn't licence you to do what you want anyway?. BUT, it would give you an understanding of the process and what's involved.

To do it reliably, at any time, your best bet would be a geostationary satellite, and UHF or Microwave links to it.

But ALL radio systems capable of doing this are going to require licencing, which would probably NOT be available to you.

What are you trying to do anyway?, as already suggested it's fairly simple to do this over the Internet, and everything is already in place.

 

[hybridmetta]

Well first of all thanks to everyone that gave me a bit of their time.
And Nigel Goodwin... well yes im not exacly a radio god. The only kind of projects related to radio i developed were related to low power fm and am transmitters. I used one of this transmitters and a preamplifier to connect to my guitar and hear what i was playing on the radio. Of course it had a bit of noise and the range was around 10 meters i think.
i don't think this project would be that hard to build with the right orientation. i started with electronics some years ago. and in a few months i will go to university to take a course on electronics and then i will have access to much more material. i think that i still need to learn some basics... maybe learn the ohm's law again :? ...

Anyway, i think that my main issue was the vco. And John, is it really possible to have all this range with just 7 or 8 watts? I have a schematic for a 500 watts hf amplifier... it sounds like it would do the job.

next tuesday i will contact ANACOM. I think they will give me a hand with the legal/ilegal issue.

For this project i wanted to use a frequency between 3 and 30 Mhz. And cuz the best frequency for this range will change during the day i thought that i could use a vco controled by a pic16f877.

i will also ask ANACOM for that ham radio licence. i think they will give me a good orientation.

And to asnwer to your question Nigel Goodwin, the main reason for this project is to be able to talk with a person that lives in canada. I wanted to be able to talk with this person at any time of the day, but i know that if im gonna use the ionosphere to do this i will only be able to talk at a certain time and maybe only at certain days of the year.

Anyone has any other idea on how i can talk with this person without using the internet or phones?

Or maybe some kinda of walkie-talkies that have this amount of range? Maybe some kinda of portable sattelite communication phones?
I know this may sound a bit strange... and well... even a bit childish but well its for a good reason.

Thanks everyone for your asnwer. Special thanks to John :!: You gave me a bit hope

 

[Nigel Goodwin]

If that's the only reason for it, then the very simple answer is to both take your RAE and talk via HF radio, by suitable selection of times and bands you should be able to talk at least once every day - probably more, by changing bands and talking later on as conditions change. It doesn't really matter how much power you throw at it, you can't over come the laws of physics.

There's no real need (or use?) for a PIC, and you may as well just buy transceivers?, a multi-band SSB transceiver isn't a project for a beginner.

But far simpler and more reliable would be to talk via the internet, if you are both on broadband there's no cost to do so, and you can send video as well.

As for the 7W CB job, as I mentioned before, it's entirely true - but only occurs during high sunspot cycles, once every seven years or so. The snag is it's completely unusable then, because you can hear signals from everywhere!.

We used to have licenced VHF radio transmitters in the vans at work, they uses 76.0625MHz and 86.0625MHz - during certain conditions they were unusable because all you could hear was New York taxis!.

 

[hybridmetta]

Ok i understand what you mean... but i wanted to use the pic16f877 so i could be able to display all the information on an graphical lcd and be able to control the vco at the same time.

As for the frequency, well i was thinking of something between 3 and 30 Mhz. I read some papers on radio propagation using the ionosphere and it seems to me that it is kinda reliable. Im not saying it wont have lots of noise but i think that using suitable noise filters im able to hear a "clear" human voice.

Thanks for your answer

 

[Nigel Goodwin]

Ok i understand what you mean... but i wanted to use the pic16f877 so i could be able to display all the information on an graphical lcd and be able to control the vco at the same time.

Any modern HAM transceiver will already use a PLL and a VCO, and will give a display of some kind - most probably LCD.

As for the frequency, well i was thinking of something between 3 and 30 Mhz. I read some papers on radio propagation using the ionosphere and it seems to me that it is kinda reliable. Im not saying it wont have lots of noise but i think that using suitable noise filters im able to hear a "clear" human voice.

Yes, it's quite usable, but ONLY at specific times and on specific bands, you can't use "something between 3 and 30 Mhz", radio hams are allocated certain small sections in that very wide spectrum. Transmitting outside that, or without a radio amateur licence, is highly frowned on - the second would get you prosecuted (and licenced hams are adept at direction finding), the first could be potentially FAR more serious, depending where you are in the world?. In many countries an unlicenced transmitter wiping out military frequencies could easily be shot!.

It's common practice to sit and wait for a particular band to come to life for a specific destination, then you communicate until it fades off again. You might then move to a different band and wait for that to come up, times and bands to specific destinations are well known amongst active radio hams.

 

[hybridmetta]

I see... maybe its a good idea to first make a call to ANACOM to make sure im not making anything ilegal. And i will try to search the net for HAM transceivers. Thanks for your time. I really apreciated that :!:

 

[Nigel Goodwin]

I see... maybe its a good idea to first make a call to ANACOM to make sure im not making anything ilegal. And i will try to search the net for HAM transceivers. Thanks for your time. I really apreciated that :!:

I think you're going to be VERY surprised how complicated such a transceiver is to make!, not to mention difficult to align once built!.

As you mention ANACOM, am I to assume you're in Portugal?.

 

[hybridmetta]

Yes i live in Portugal. I was born here. Lots of ppl told me this was gonna be hard and that maybe it was a good idea to spend the first 2 years on university studying and going to the library often. Maybe i should listen to them :?

Anyway, i was always very interested in electronics (specialy robotic) and informatic. A year ago i made a pic16f84a based robot that was controlled by the serial port of my computer and a program made using Visual Basic. The code running on the pic was made using pic basic.

I never thought it would be easy... but i didn't think it would be so hard...

Well i think i have plenty of time to learn... and i have all the motivation and dedication in the world. so maybe in 2 years i will be able to make this circuit.

By the way i used to use Tina so simulate my circuits, Eagle to make the boards and icprog to program my pics. Did you ever use any of those? Do you recomend any other software that might be usefull?

 

[Nigel Goodwin]

Yes i live in Portugal. I was born here. Lots of ppl told me this was gonna be hard and that maybe it was a good idea to spend the first 2 years on university studying and going to the library often. Maybe i should listen to them :?

I reversed your IP address, it says Portugal as well 8)

I would rate it as considerably harder to build than your own TV set, and (like building your own TV) it's likely to cost you considerably more than buying one!.

Anyway, i was always very interested in electronics (specialy robotic) and informatic. A year ago i made a pic16f84a based robot that was controlled by the serial port of my computer and a program made using Visual Basic. The code running on the pic was made using pic basic.

I never thought it would be easy... but i didn't think it would be so hard...

Well i think i have plenty of time to learn... and i have all the motivation and dedication in the world. so maybe in 2 years i will be able to make this circuit.

Yes, it's not something to try BEFORE you do an electonics course, after two years (presumably full time?), you should have more of an understanding of what's involved.

I'd still advise you to take your RAE, it's the only way you would be able to do it legally (and your brother needs to as well). It would also help you greatly on your electronics course, which probably won't touch on radio a great deal!.

By the way i used to use Tina so simulate my circuits, Eagle to make the boards and icprog to program my pics. Did you ever use any of those? Do you recomend any other software that might be usefull?

As I'm the author of WinPicProg I use that to program PIC's :lol:

I don't use simulators, nor make PCB's, so I don't use either of those.

 

[hybridmetta]

It's interesting that you traced my ip... but im sure you also know i could be using a proxie... don't you think that's possible? 8)

Harder then building a tv set... well maybe... i know a person who did it... that person is helping me... but if you say so...

And yes im going to the university now. The course is 5 years... but im not realy a n00b. of course im not exacly an expert... lets just say that usualy im the one fixing the computers and devices on the neightborhood 8) lol

I tryed your program once but it didn't work with my jdm programmer. it's a TE21SE AP sold by some spanish company or something. Maybe i should buy another programmer

 

[Nigel Goodwin]

Harder then building a tv set... well maybe... i know a person who did it... that person is helping me... but if you say so...

What did he build?, a multi-band SSB transceiver?. Many radio amateurs world wide have built them, but not so many these days, due to the high quality and cheap price of commercial ones.

I tryed your program once but it didn't work with my jdm programmer. it's a TE21SE AP sold by some spanish company or something. Maybe i should buy another programmer

I don't support serial port programmers, specifically because of the unreliability of the JDM - you might notice the the author of ICProg doesn't offer program support, whereas I do - I suspect this is because of the JDM support issues.

As long as your programmer is working I should stick with it, ICProg is a good program - I even have it installed here as well :lol: Interestingly it uses (or at least did use!) my old 16 bit disassembler, I've always assumed it was perhaps based on my old 16 bit code?, ICProg didn't appear until well after I had released my 16 bit source.

 

[hybridmetta]

I don't really know what he built. lol. Maybe i should do my homework on this. He said it wasn't that easy. Maybe i should buy some more books on this subject.

What language do you use to compile winprog? in visual basic there is some ocx called comm control (mscomm32.ocx) used to send and receive data from serial ports. maybe you could make a version of your software in visual basic :roll: it would be really cool :!:

And this programmer as given me some problems before. some of the pics i bought simply stoped working maybe cause of this programmer.

In case you are interested here are some info concerning to things related to this device:

-the lcd controller is a **broken link removed** (same used in nokia cellphones);
-i thought that maybe i could use an **broken link removed** (or this one)
-the amplifier would probably be **broken link removed**
-i use a program called **broken link removed** to predict the propagation
-and probably i would use an **broken link removed**

thanks again for your time

 

[audioguru]

Your oscillator circuits are not Voltage Controlled VCO's. They are just fixed-audio-frequency tone generators. They probably won't work above 20kHz.

You need a stable (crystal) RF carrier oscillator and a modulator. Then you will be able to use the amplifier to blast a high-power radio signal down the street. :lol:

 

[hybridmetta]

ummm... i guess i didn't notice that... so do you know any vco that may be suitable for this project? maybe something based on a varator diode?

 

[audioguru]

Varactor diodes change capacitance with temperature. Their drift doesn't matter with wideband FM broadcast band receivers. Yours will be narrow-band and you probably need a crystal-controlled frequency synthesizer circuit if you want to change the carrier frequency and still have stable frequencies.
I was a ham but never a radio ham so maybe someone else can help you. :lol: